Borehole acoustic source

Abstract

The present invention discloses an acoustic borehole source and method of using the source for generating elastic waves through an earth formation that may be used for logging or permanent installations. The acoustic source is comprised of a first motorized reaction mass and at least two pads, each pad connected to the sonde and the motorized reaction mass using pushing rods. In an alternate embodiment, the source has a first and second motorized reaction mass and at least two pads. The motorized reaction masses may be activated to allow the pads to move at an angle α relative to the axis of the sonde. In a third embodiment, the acoustic borehole source includes additional pairs of motorized reaction masses so that pads may be independently activated.

1. An acoustic borehole source for generating elastic waves through an earth formation at a designated location via a wall comprising:
 a first motorized reaction mass positioned along an axis of a sonde; and 
 at least two pads, wherein each of said at least two pads are connected to said sonde and said first motorized reaction mass using a plurality of variable angle pushing rods to convert an axial motion into a radial motion so that said at least two pads generate elastic waves through the earth formation upon activation of said first motorized reaction mass as a result of impact of the pads against the wall; 
 wherein the impedance of the acoustic borehole source may be controlled using said plurality of variable angle pushing rods; 
 wherein activation of said first motorized reaction mass provides variable location adjustment for said at least two pads while said at least two pads are positioned at the designated location of the acoustic borehole source, such that said at least two pads generate elastic waves through the earth formation at multiple locations while at the designated location. 
 
   
   
     2. The acoustic borehole source of  claim 1 , further comprising anchoring means to anchor said sonde in a borehole located in the earth formation. 
   
   
     3. The acoustic borehole source of  claim 1 , wherein at least two of said pads are used to anchor said sonde in a borehole located in the earth formation. 
   
   
     4. The acoustic borehole source of  claim 1 , further comprising a receiver array positioned along said sonde for receiving said elastic waves after said elastic waves have passed through a portion of said earth formation. 
   
   
     5. The acoustic borehole source of  claim 1 , wherein said plurality of pushing rods are hingedly connected to the first reaction mass and the pads. 
   
   
     6. The acoustic borehole source of  claim 1 , wherein the weight of the motorized reaction masses are designed to accommodate a specific source property, wherein said source property is selected from the group consisting of radiation energy, frequency bandwidth, and resonance frequency. 
   
   
     7. The acoustic borehole source of  claim 1 , wherein the stiffness of the motorized reaction masses are designed to accommodate a specific source property, wherein said source property is selected from the group consisting of radiation energy, frequency bandwidth, and resonance frequency. 
   
   
     8. An acoustic borehole source for generating elastic waves through an earth formation at a designated location via a wall comprising:
 a first motorized reaction mass and a second motorized reaction mass positioned along an axis of a sonde; and 
 at least two pads, wherein each of said at least two pads are connected to said first motorized reaction mass and said second motorized reaction mass using a plurality of variable angle pushing rods to convert an axial motion into a radial motion, so that said at least two pads generate elastic waves through the earth formation upon activation of at least one of said first and second motorized reaction masses as a result of impact of the pads against the wall; 
 wherein the impedance of the acoustic borehole source may be controlled using said plurality of variable angle pushing rods; 
 wherein activation of said first motorized reaction mass provides variable location adjustment for said at least two pads while said at least two pads are positioned at the designated location of the acoustic borehole source, such that said at least two pads generate elastic waves through the earth formation at multiple locations while at the designated location. 
 
   
   
     9. The acoustic borehole source of  claim 8 , wherein said first and second motorized reaction masses are connected to opposite ends of each pad of said at least two pads using said pushing rods such that said pads move at an angle α relative to said axis of said sonde. 
   
   
     10. The acoustic borehole source of  claim 9 , further comprising a compression spring connecting said first and second motorized reaction masses. 
   
   
     11. The acoustic borehole source of  claim 8 , comprising at least three pads and a third and fourth motorized reaction masses, wherein at least two of said at least three pads are commonly connected at opposite ends to said first and second motorized reaction masses using a first plurality of pushing rods and wherein at least one of said at least three pads is connected at opposite ends to said third and fourth motorized reaction masses using a second plurality of pushing rods. 
   
   
     12. The acoustic borehole source of  claim 8 , further comprising anchoring means to anchor said sonde in a borehole within the earth formation. 
   
   
     13. The acoustic borehole source of  claim 8 , wherein at least two of said pads are used to anchor said sonde in a borehole within the earth formation. 
   
   
     14. The acoustic borehole source of  claim 13 , further comprising a receiver array positioned along said sonde for receiving said elastic waves after said elastic waves have passed through a portion of said earth formation. 
   
   
     15. The acoustic borehole source of  claim 8 , wherein said plurality of pushing rods are hingedly connected to the first reaction mass and the at least two pads. 
   
   
     16. The acoustic borehole source of  claim 8 , wherein the weight of the motorized reaction masses are designed to accommodate a specific source property, wherein said source property is selected from the group consisting of radiation energy, frequency bandwidth, and resonance frequency. 
   
   
     17. The acoustic borehole source of  claim 8 , wherein the stiffness of the motorized reaction masses are designed to accommodate a specific source property, wherein said source property is selected from the group consisting of radiation energy, frequency bandwidth, and resonance frequency. 
   
   
     18. An acoustic borehole source for generating elastic waves through an earth formation at a designated location via a wall comprising:
 a first motorized reaction mass positioned along an axis of a borehole; 
 at least two pads, wherein each of said at least two pads are connected to said first motorized reaction mass and said borehole using a plurality of variable angle pushing rods to convert an axial motion into a radial motion, so that said at least two pads generate elastic waves through the earth formation upon activation of said first motorized reaction mass as a result of contact of the pads with the wall; and 
 wherein the impedance of the acoustic borehole source may be controlled using said plurality of variable angle pushing rods; 
 wherein activation of said first motorized reaction mass provides variable location adjustment for said at least two pads while said at least two pads are positioned at the designated location of the acoustic borehole source, such that said at least two pads generate elastic waves through the earth formation at multiple locations while at the designated location. 
 
   
   
     19. The acoustic borehole source of  claim 18 , further comprising a receiver array positioned along said borehole for receiving said elastic waves after said elastic waves have passed through a portion of said earth formation. 
   
   
     20. The acoustic borehole source of  claim 18 , wherein said plurality of pushing rods are hingedly connected to the first reaction mass and the at least two pads. 
   
   
     21. The acoustic borehole source of  claim 18 , wherein the weight of the motorized reaction masses are designed to accommodate a specific source property, wherein said source property is selected from the group consisting of radiation energy, frequency bandwidth, and resonance frequency. 
   
   
     22. The acoustic borehole source of  claim 18 , wherein the stiffness of the motorized reaction masses are designed to accommodate a specific source property, wherein said source property is selected from the group consisting of radiation energy, frequency bandwidth, and resonance frequency. 
   
   
     23. An acoustic borehole source for generating elastic waves through an earth formation at a designated location via a wall comprising:
 a first motorized reaction mass and a second motorized reaction mass positioned along an axis of a borehole; and 
 at least two pads, wherein each of said at least two pads are connected to said first motorized reaction mass and said second motorized reaction mass using a plurality of variable angle pushing rods to convert an axial motion into a radial motion, so that said at least two pads generate elastic waves through the earth formation upon activation of at least one of said first and second motorized reaction masses as a result of contact of the pads with the wall; 
 wherein the impedance of the acoustic borehole source may be controlled using said plurality of variable angle pushing rods; 
 wherein activation of said first motorized reaction mass provides variable location adjustment for said at least two pads while said at least two pads are positioned at the designated location of the acoustic borehole source, such that said at least two pads generate elastic waves through the earth formation at multiple locations while at the designated location. 
 
   
   
     24. The acoustic borehole source of  claim 23 , wherein said first and second motorized reaction masses are connected to opposite ends of each pad so that said pads move at an angle α relative to said axis of the borehole. 
   
   
     25. The acoustic borehole source of  claim 24 , further comprising a compression spring connecting said first and second motorized reaction masses. 
   
   
     26. The acoustic borehole source of  claim 23 , comprising at least three pads and a third and fourth motorized reaction masses, wherein at least two of said at least three pads are commonly connected at opposite ends to said first and second motorized reaction masses using a first plurality of pushing rods and wherein at least one of said at least three pads is connected at opposite ends to said third and fourth motorized reaction masses using a second plurality of pushing rods. 
   
   
     27. The acoustic borehole source of  claim 23 , further comprising a receiver array positioned along said borehole for receiving said elastic waves after said elastic waves have passed through a portion of said earth formation. 
   
   
     28. The acoustic borehole source of  claim 23 , wherein said plurality of pushing rods are hingedly connected to the first reaction mass and the at least two pads. 
   
   
     29. The acoustic borehole source of  claim 23 , wherein the weight of the motorized reaction masses are designed to accommodate a specific source property, wherein said source property is selected from the group consisting of radiation energy, frequency bandwidth, and resonance frequency. 
   
   
     30. The acoustic borehole source of  claim 23 , wherein the stiffness of the motorized reaction masses are designed to accommodate a specific source property, wherein said source property is selected from the group consisting of radiation energy, frequency bandwidth, and resonance frequency. 
   
   
     31. A method of generating elastic waves through an earth formation at a designated location via a wall comprising:
 a. providing a sonde having an acoustic borehole source comprised of a first motorized reaction mass positioned along an axis of said sonde and at least two pads, wherein each of said at least two pads are connected to said sonde and said first motorized reaction mass using a plurality of variable angle pushing rods so as to convert an axial motion into a radial motion wherein the impedance of the acoustic borehole source may be controlled using said plurality of variable angle pushing rods; 
 b. anchoring said sonde at a selected position within a borehole located within the earth formation; 
 c. activating said first motorized reaction mass so that at least one of said at least two pads urges against a wall of said borehole to generate elastic waves into the earth formation as a result of impact of the pad against the wall; and 
 wherein activation of said first motorized reaction mass provides variable location adjustment for said at least two pads while said at least two pads are positioned at the designated location of the acoustic borehole source, such that said at least two pads generate elastic waves through the earth formation at multiple locations while at the designated location. 
 
   
   
     32. The method of  claim 31 , further comprising receiving said elastic waves after said elastic waves have passed through a portion of said earth formation. 
   
   
     33. The method of  claim 31 , wherein anchoring said sonde comprises urging at least two of said pads against said borehole wall. 
   
   
     34. A method of generating elastic waves through an earth formation at a designated location via a wall comprising:
 a. providing a sonde having an acoustic borehole source comprised of a first and a second motorized reaction masses positioned along an axis of said sonde and at least two pads, wherein each of said at least two pads are connected to said first motorized reaction mass and said second motorized reaction mass using a plurality of variable angle pushing rods so as to convert an axial motion into a radial motion wherein the impedance of the acoustic borehole source may be controlled using said plurality of variable angle pushing rods; 
 b. anchoring said sonde at a selected position within the a borehole within the earth formation; and 
 c. preferentially activating said first or second motorized reaction masses so that at least one of said at least two pads urges against a wall of the borehole to generate elastic waves into the earth formation as a result of impact of the pad against the borehole wall, wherein direction of the elastic waves is a function of phase of activation of the first motorized reaction mass relative to the second motorized reaction mass; 
 wherein activation of said first motorized reaction mass provides variable location adjustment for said at least two pads while said at least two pads are positioned at the designated location of the acoustic borehole source, such that said at least two pads generate elastic waves through the earth formation at multiple locations while at the designated location. 
 
   
   
     35. The method of  claim 34 , further comprising coordinating the activation of said first or second motorized reaction masses so that at least one of said pads urges against said borehole wall at a predetermined angle α relative to the axis of said sonde. 
   
   
     36. The method of  claim 34 , wherein anchoring said sonde comprises urging at least two of said pads against said borehole wall. 
   
   
     37. A method of generating elastic waves through an earth formation at a designated location via a wall comprising:
 a. providing a sonde having an acoustic borehole source comprised of a first, second, third and fourth motorized reaction masses positioned along an axis of said sonde and at least three pads, wherein at least two of said pads are commonly connected at opposite ends to said first and second motorized reaction masses using a first plurality of variable angle pushing rods that convert an axial motion into a radial motion and wherein at least one of said pads is connected at opposite ends to said third and fourth motorized reaction masses using a second plurality of variable angle pushing rods that convert an axial motion into a radial motion wherein the impedance of the acoustic borehole source may be controlled using said plurality of variable angle pushing rods; 
 b. anchoring said sonde at a selected position within a borehole located within the formation; and 
 c. preferentially activating said first, second, third or fourth motorized reaction masses so that at least one of said at least two pads urges against a wall of the borehole to generate elastic waves through said earth formation as a result of impact of the pad against the borehole wall, wherein direction of the elastic waves is a function of phase of activation of the first, second, third and fourth motorized reaction masses relative to each other; 
 wherein activation of said first motorized reaction mass provides variable location adjustment for said at least two pads while said at least two pads are positioned at the designated location of the acoustic borehole source, such that said at least two pads generate elastic waves through the earth formation at multiple locations while at the designated location. 
 
   
   
     38. The method of  claim 37 , further comprising receiving said elastic waves after said elastic waves have passed through a portion of said earth formation. 
   
   
     39. The method of  claim 37 , further comprising coordinating the activation of said first, second, third and fourth motorized reaction masses so that at least one of said pads urges against said borehole wall at a predetermined angle α relative to the axis of said sonde. 
   
   
     40. The method of  claim 37 , wherein anchoring said sonde comprises urging at least two of said pads against said borehole wall. 
   
   
     41. A method of generating elastic waves through an earth formation at a designated location comprising:
 a. positioning an acoustic borehole source along a borehole wall in the earth formation wherein said acoustic borehole source is comprised of a first motorized reaction mass positioned along an axis of said borehole wall and at least two pads, wherein each of said at least two pads are connected to said sonde and said first motorized reaction mass using a plurality of variable angle pushing rods to convert an axial motion into a radial motion, wherein the impedance of the acoustic borehole source may be controlled using said plurality of variable angle pushing rods; and 
 b. activating said first motorized reaction mass so that at least one of said at least two pads urges against said borehole wall to generate elastic waves into the earth formation as a result of impact of the pad against the borehole wall; 
 wherein activation of said first motorized reaction mass provides variable location adjustment for said at least two pads while said at least two pads are positioned at the designated location of the acoustic borehole source, such that said at least two pads generate elastic waves through the earth formation at multiple locations while at the designated location. 
 
   
   
     42. The method of  claim 41 , further comprising receiving said elastic waves after said elastic waves have passed through a portion of said earth formation. 
   
   
     43. A method of generating elastic waves through an earth formation at a designated location comprising:
 a. positioning an acoustic borehole source along a borehole wall in the earth formation wherein said acoustic borehole source is comprised of a first and a second motorized reaction masses positioned along an axis of said borehole wall and at least two pads, wherein each of said at least two pads are connected to said first motorized reaction mass and said second motorized reaction mass using a plurality of variable angle pushing rods to convert an axial motion into a radial motion, wherein the impedance of the acoustic borehole source may be controlled using said plurality of variable angle pushing rods; and 
 b. preferentially activating said first or second motorized reaction masses so that at least one of said at least two pads urges against said borehole wall to generate elastic waves into the earth formation as a result of impact of the pad against the borehole wall, wherein direction of the elastic waves is a function of phase of activation of the first motorized reaction mass relative to the second motorized reaction mass; 
 wherein activation of said first motorized reaction mass provides variable location adjustment for said at least two pads while said at least two pads are positioned at the designated location of the acoustic borehole source, such that said at least two pads generate elastic waves through the earth formation at multiple locations while at the designated location. 
 
   
   
     44. The method of  claim 43 , further comprising coordinating the activation of said first or second motorized reaction masses so that at least one of said pads urges against said borehole wall at a predetermined angle α relative to the axis of said borehole. 
   
   
     45. A method of generating elastic waves through an earth formation at a designated location comprising:
 a. positioning an acoustic borehole source along a borehole wall in the earth formation wherein said acoustic borehole source is comprised of a first, second, third and fourth motorized reaction masses positioned along an axis of said borehole wall and at least three pads, wherein at least two of said pads are commonly connected at opposite ends to said first and second motorized reaction masses using a first plurality of variable angle pushing rods to convert an axial motion into a radial motion and wherein at least one of said pads is connected at opposite ends to said third and fourth motorized reaction masses using a second plurality of variable angle pushing rods to convert an axial motion into a radial motion, wherein the impedance of the acoustic borehole source may be controlled using said plurality of variable angle pushing rods; 
 b. anchoring said sonde at the designated location within the borehole wall; and 
 c. preferentially activating said first, second, third or fourth motorized reaction masses so that at least one of said at least two pads urges against said borehole wall to generate elastic waves through said earth formation as a result of impact of the pad against the borehole wall, wherein direction of the elastic waves is a function of phase of activation of the first, second, third and fourth motorized reaction masses relative to each other; 
 wherein activation of said first motorized reaction mass provides variable location adjustment for said at least two pads while said at least two pads are positioned at the designated location of the acoustic borehole source, such that said at least two pads generate elastic waves through the earth formation at multiple locations while at the designated location. 
 
   
   
     46. The method of  claim 45 , further comprising receiving said elastic waves after said elastic waves have passed through a portion of said earth formation. 
   
   
     47. The method of  claim 45 , further comprising coordinating the activation of said first, second, third and fourth motorized reaction masses so that at least one of said pads urges against said borehole wall at a predetermined angle α relative to the axis of said borehole. 
   
   
     48. The acoustic borehole source of  claim 1 , wherein the impedance of the acoustic borehole source may be controlled using said plurality of variable angle pushing rods such that a first individual variable angle pushing rod and a second individual variable angle pushing rod of said plurality of variable angle pushing rods have an ability to have different angles relative to said axis of said sonde. 
   
   
     49. The acoustic borehole source of  claim 8 , wherein such that a first individual variable angle pushing rod and a second individual variable angle pushing rod of said plurality of variable angle pushing rods have an ability to have different angles relative to said axis of said sonde. 
   
   
     50. The acoustic borehole source of  claim 18 , wherein the impedance of the acoustic borehole source may be controlled using said plurality of variable angle pushing rods such that a first individual variable angle pushing rod and a second individual variable angle pushing rod of said plurality of variable angle pushing rods have an ability to have different angles relative to said axis of said borehole. 
   
   
     51. The acoustic borehole source of  claim 23 , wherein the impedance of the acoustic borehole source may be controlled using said plurality of variable angle pushing rods such that a first individual variable angle pushing rod and a second individual variable angle pushing rod of said plurality of variable angle pushing rods have an ability to have different angles relative to said axis of said borehole. 
   
   
     52. The method of  claim 31 , wherein the impedance of the acoustic borehole source may be controlled using said plurality of variable angle pushing rods such that a first individual variable angle pushing rod and a second individual variable angle pushing rod of said plurality of variable angle pushing rods have an ability to have different angles relative to said axis of said sonde. 
   
   
     53. The method of  claim 34 , wherein the impedance of the acoustic borehole source may be controlled using said plurality of variable angle pushing rods such that a first individual variable angle pushing rod and a second individual variable angle pushing rod of said plurality of variable angle pushing rods have an ability to have different angles relative to said axis of said sonde. 
   
   
     54. The method of  claim 37 , wherein the impedance of the acoustic borehole source may be controlled using said plurality of variable angle pushing rods such that a first individual variable angle pushing rod and a second individual variable angle pushing rod of said plurality of variable angle pushing rods have an ability to have different angles relative to said axis of said sonde. 
   
   
     55. The method of  claim 41 , wherein the impedance of the acoustic borehole source may be controlled using said plurality of variable angle pushing rods such that a first individual variable angle pushing rod and a second individual variable angle pushing rod of said plurality of variable angle pushing rods have an ability to have different angles relative to said axis of said borehole wall. 
   
   
     56. The method of  claim 43 , wherein the impedance of the acoustic borehole source may be controlled using said plurality of variable angle pushing rods such that a first individual variable angle pushing rod and a second individual variable angle pushing rod of said plurality of variable angle pushing rods have an ability to have different angles relative to said axis of said borehole wall. 
   
   
     57. The method of  claim 45 , wherein the impedance of the acoustic borehole source may be controlled using said plurality of variable angle pushing rods such that a first individual variable angle pushing rod and a second individual variable angle pushing rod of said plurality of variable angle pushing rods have an ability to have different angles relative to said axis of said borehole wall.